The present invention relates generally to a joint implant.
Such joint implants are used for instance as intervertebral disk prostheses for interconnecting adjacent vertebrae in an articulated manner. The implant can have one or more joint regions that afford an articulated motion of the respective parts of the implant to each other and independently from each other, for instance pivoting or tilting motions against each other. The implant can thus have two different joint regions, each of which performs pivoting or tilting motions about a pivoting or tilting axis that is arranged in a plane transverse to the longitudinal axis of the implant, the two axes being arranged at an angle to each other.
For adapting the implant to the respective anatomical conditions while affording easy handling of the implant preparatory to its implantation and also during the implantation, it turned out to be advantageous for the upper and/or lower implant part to include a joint part on the one side, the joint part providing the joint region of the respective implant part so that the two adjacent joint regions of the two implant parts or the respective joint region of the implant plant together with the abutment surface of the intermediate part form an articulated connection. Thus, the implant can be easily configured in such a manner that it suits different bones with differently large implant abutment surfaces and/or different distances of the bone connecting regions to each other, namely by selecting suitable joint parts. The joint can be adapted in an easy manner to patients with differently sized vertebrae and/or to patients with different weights.
Furthermore, on the one side the various implant parts are required to be fixed to each other for allowing the implant to be implanted as a pre-mounted assembly, which makes the implantation considerably easier. On the other side, the connection between the individual implant parts is required to resist high mechanical loads over a longest possible period of time because the implant is subject to high forces that are exerted while the respective patient moves and also because the implant parts must perform complex combined motions relative to each other, e.g. pivoting motions, torsional motions, combined pivoting and torsional motions or the like, as a result of complex motions of the patient. The connection of the implant parts must be durable even in the case of such complex motions and under high forces.
Further, such an implant or its individual component parts must be easy sterilizing.
An implant of the kind which has been described is known from DE 20 2008 012 749, in which the upper and the lower implant part each consist of a joint part and an abutment part that can be abutted on the respective bone, the parts being connected to each other to form a coherent assembly by means of a connecting element. To this end, the joint part is moved into a laterally open recess, with the insertion direction lying in a plane parallel to the two main planes of the two components, and the joint part is then fixed to the abutment part in such a manner that it is secured against sliding by means of a snap connection. While such an implant has delivered satisfying performance on various occasions, the disadvantage of that implant is that the implanted implant parts and abutment parts may become detached from each other during complex motions of a patient, which involves the risk of injury, particularly spinal injuries. Solving this problem by making the snap connection between the joint parts and the abutment parts more robust has turned out to be infeasible because this also impedes the mounting of the implant.
Accordingly, it is an objective of the present invention to provide an implant of the above-described kind which has a long service life and can be easily mounted also under the influence of high forces and complex motion profiles. It also is an objective of the present invention to provide a device which simplifies mounting of the implant. The present invention accomplishes the above objectives.